(1) Field of the Invention
This invention relates to an apparatus for feeding documents from a stack of documents, in single file, into a document track, with the apparatus employing a variable load applicator and an endless belt.
(2) Background Information
The purpose of a document feeder of the type mentioned is to separate or pick a document from a stack of documents in a hopper and feed it at a particular rate with an inter-document gap between documents to a downstream module like a reader, encoder, endorser, microfilmer, or a pocket module, for example.
Feeding a single document from a stack of documents generally requires advancing the first document in the stack, while inhibiting the remainder of the documents in the stack by a retard mechanism. The next document in the stack follows the trailing edge of the prior document which was just removed from the stack.
In some prior art designs, the retard mechanism used a roller which operated in a direction which was opposite to the direction of the associated feed roller. Such a design generally required a separate motor for the feed roller and a separate motor for the retard roller.
When feed and retard rollers are used, it is generally necessary to be very precise in the adjustment of the rollers relative to each other. As the rollers begin to wear, additional maintenance or adjustment is necessary. Replacing such feed and retard rollers, when excessively worn, generally requires that the maintenance be done by a service person. Very often, the feed and retard rollers become "glazed" or slippery in use, and consequently, they lose their effectiveness.
The hopper module which contains the stack of documents to be fed generally uses gravity and a spring to feed the documents in the stack to a point where the first document in the stack can be picked from the stack and fed into the document track. One of the problems in designing the hopper module is that it is difficult to maintain a constant pressure on the first document to be picked from the stack as the size of the stack changes from a full stack to one which is one quarter full, for example. When the pressure is not constant, misfeeds or nonfeeds result.